Replace Enum with StrEnum for string-based enums

[masoudghah]

Currently, in the Pydantic section, the example defines a string-based enum as:

from enum import Enum

class MusicBand(str, Enum):
    AEROSMITH = "AEROSMITH"
    QUEEN = "QUEEN"
    ACDC = "AC/DC"

A better approach in Python 3.11+ is to use StrEnum, which avoids the need for multiple inheritance (str, Enum) and makes the intent clearer:

from enum import StrEnum

class MusicBand(StrEnum):
    AEROSMITH = "AEROSMITH"
    QUEEN = "QUEEN"
    ACDC = "AC/DC"